It is common practice to use irrigation fluids (e.g., 0.9% or other concentration sodium chloride, lactated Ringer's solutions, etc.) to wash out debris, blood, tissue, fat or unwanted body fluids during surgeries on human. Antibiotic irrigation fluids are also used during surgery to prevent infection.
Such irrigation fluids are sold in flexible packages and semi-rigid and rigid glass and plastic bottles. However, such irrigation fluids may cause problems if they are not maintained at a proper temperature.
“Thermoregulation” is a human body's way to maintain homeostasis by keeping body temperature between certain boundaries regardless of temperatures in the external environment. “Normothermia” for a human body includes a core temperature in the range of about 36° C. to 38° C. (96.8° F. to 100.4° F.). “Hypothermia” for a human body includes a core temperature less than about 36° C. (96.8° F.).
Inadvertent “perioperative hypothermia” is a common but preventable complication of surgical procedures. Surgical patients are at risk of developing hypothermia at any stage of the perioperative pathway.
If the human body is unable to maintain a certain temperature, due to external stressors such as anesthesia, or use of cold Intravenous (IV) and irrigation fluids during a surgery, “homeostatic imbalance” occurs. It has been widely recognized and reported that “perioperative hypothermia” is a contributing factor in the development of surgical site infections, also contributing to longer length of hospital stay and an increased risk for mortality during and after surgery.
There is abundant research showing increased patient risks intra and post operatively associated with a drop in core body temperature during the surgical procedure. Heat loss occurs through different mechanisms including conduction loss, convection loss and radiated heat loss. Open wounds present a challenge because large surface areas with abundant blood supply speed up the heat loss to an environment cooler than body temperature.
One study published in the journal Anesthesiology revealed that less than one degree of hypothermia is enough to “significantly increase blood loss during surgery,” while other published studies indicate that a similar degree of hypothermia is also enough to significantly increase the need for blood transfusions.
Virtually any patient regardless of age, race, gender, health and fitness status, and length or type of procedure is at risk for surgery-related hypothermia. The reason being is hypothermia is a body's normal reaction to the induction of anesthesia. When anesthesia is administered, or cool/cold IV and irrigation fluids are used, core-to-peripheral redistribution of body heat occurs, which lowers overall body temperature. Post anesthetic shivering is also one of the leading causes of discomfort for patients recovering from general anesthesia. The causes of shivering primarily include hypothermia from thermoregulation inhibition by anesthetics.
Irrigation fluids used to irrigate/wash a body cavity during a surgery include moderate (500 mls to 1000 mls) to volumes large volumes including those greater than 2000 mls, are routinely used.
Using cool or cold IV or irrigation fluids in a patient during a surgery further aggravates perioperative hypothermia symptoms.
The, temperatures in operating rooms are typically set in the range of 60° F. (16° C.) to 70° F. (21° C.), which is cold compared to normal body temperatures of 98.6° F. IV and irrigation fluids are often placed in basins or other single walled containers without covers in an operating room during a surgery. The fluids are often cooled very quickly to way below normal body temperature (98.6° F., 37° C.) because most operating rooms include cooling air flows (e.g., air conditioning, etc.).
Irrigating solutions are kept in warming units at about 108° F. (37° C.). The solution is. poured into an open top basin or single walled containers and is kept on aback table that holds the surgical instruments. When the solution is needed it is poured into the wound from the container or flushed using a bulb syringe. Most of the time the solution sitting in the open container loses heat and often approaches the ambient room temperature of the operating room, which is about 60° F. (16° C.) to 70° F. (21° C.).
The irrigating solutions in basins or single walled containers very often distinctly cold to the touch. The solution becomes a heat sink that robs the body of heat making it more difficult to maintain a normal body temperature during a surgery further aggravates perioperative hypothermia symptoms. The longer the surgical procedure and the larger the wound the greater the potential heat loss.
One of the most common interventions used to prevent perioperative hypothermia is warming IV and irrigation solutions. Fluids for irrigation may be warmed in devices up to 110° F., (43° C.).
One study has shown that patients with warmed IV and irrigation fluids demonstrated a higher core body temperature than the non-warmed: 36.8° C. (98.2° F.) versus 35.5° C. (95.9° F.). Another study has shown that irrigation with lactated Ringer's solution warmed up to 39° C. did not show any incidences of hypothermia.
There are many types of fluid warmers know in the art. They include warming basins, warming towers, warming pots, etc. in which an irrigation solution is physically placed and warming cabinets.
For example, one irrigation solution warmer includes a heated basin in which irrigation solution is placed. The device maintains irrigation solution temperatures of solution that is poured back into a table basin. However, the warmer is another device that must be purchased, maintained and its basin autoclaved and/or sterilized and requires another electrical outlet in the operating room during surgery. In addition the basin is awkward to pour irrigation solution from or extract it with an irrigation bulb syringe. Warming towers and warming pots have similar problems.
Another irrigation solution warmer includes a warming cabinet. To warm irrigation solutions, a dry warming cabinet with carefully controlled temperatures is used. The warming cabinet will be controlled by a calibrated thermometer. However, the warmer is another device that must be purchased and maintained and requires another electrical outlet in the operating room during surgery.
In addition, another problem is that during a warming period in a warming cabinet, overwrap packaging and/or pour bottles are left intact on flexible intravenous and irrigation containers to ensure sterile solution integrity. Once removed from the warming cabinet, solutions must be used within 24 hours and/or discarded, and not returned to stock supply or re-warmed. This often leads to waste of irrigation solutions.
Another problem is when a warming cabinet is used, the irrigation fluids are typically transferred to an open metal or plastic fluid basin or single walled container without a top, which is used to pour the irrigation fluids directly into a wound and/or used to extract fluids with an irrigation bulb syringe. The basin are hard to pour.
Another problem is that all types of irrigation solution warmers must have an operational check, cleaning and preventive maintenance inspection at least semiannually to ensure patient safety. The inspection includes electrical and temperature safety.
Another problem is that even if irrigation fluids are warmed by warming devices or in a warming cabinet, they cool off very rapidly in a cool operating room. Thus, even when a warming device/cabinet is used, perioperative hypothermia can occur if the fluids sit for too long a time period in the basins. A circulating surgical nurse typically has to make multiple trips to a fluid warmer (usually in an adjacent room) to keep getting irrigating solutions that are warm.
Thus, it is desirable to solve some of the many problems associated with warming irrigation fluids used for surgery on humans and help prevent perioperative hypothermia.